Conventionally, a grommet is externally fitted to a wire harness routed from an engine compartment to a passenger cabin in an automobile and is mounted in a through-hole in a vehicle body panel that partitions the engine compartment and the passenger cabin. Thereby, the wire harness inserted to the through-hole is protected, and water, dust, and sound are prevented from leaking from the engine compartment side to the passenger cabin. Further, in many cases, wire materials routed from the engine compartment to the passenger cabin, such as a hood opener cable for opening a hood, a washer hose, a circuit for dealer options, and the like, are inserted through the grommet.
Examples of grommets of this type include a grommet described in Japanese Patent Laid-Open Publication No. 2009-296741 (Patent Literature 1). As shown in FIGS. 7 to 9, a grommet 1 includes a small diameter tubular portion 2 and a large diameter tubular portion 3. The small diameter tubular portion 2 has a central through-hole 2a to which a wire harness W/H is snugly inserted. The large diameter tubular portion 3 is externally fitted so as to be concentric with the small diameter tubular portion 2 and to have a space between an increased diameter side of the large diameter tubular portion 3 and an outer peripheral surface of the small diameter tubular portion 2. On an outer peripheral surface of the increased diameter end side of the large diameter tubular portion 3, a vehicle body engagement recess 4 is provided to engage with a peripheral edge 7a of a through-hole 7 in a vehicle body panel 6 partitioning an engine compartment (X) and a passenger cabin (Y). In addition, a wire insertion tubular portion 5 projects toward a decreased diameter end side from a position off a center of the large diameter tubular portion 3, the wire insertion tubular portion 5 having a wire material, such as an opener cable, a washer hose, or the like, inserted therethrough. While a tip of the wire insertion tubular portion 5 is a closed end, a rib-shaped cut line 5a indicating a position to cut and open up the closed end is provided on an entire periphery of the wire insertion tubular portion 5. Accordingly, the closed end of the wire insertion tubular portion 5 can be opened up by making a cut at the cut line 5a when the wire material such as the cable, the hose, or the like is to be inserted.
The grommet 1 attached to the wire harness W/H is simply pressed into the through-hole 7 of the vehicle body panel 6 with the decreased diameter end side first in a direction from an engine compartment (X) to a passenger cabin (Y), as shown with arrows in FIG. 8(A). The vehicle body engagement recess 4 of the grommet 1 thus engages with the peripheral edge 7a of the through-hole 7, as shown in FIG. 8(B), and thereby, mounting of the grommet 1 in the through-hole 7 is completed.
When the grommet 1 is mounted in the through-hole 7, however, it is difficult to straightly insert the grommet 1 such that a central axis line of the grommet 1 is aligned with an axis line of the through-hole 7. The grommet 1 is thus often in a shifted state to some extent when inserted. In such a case, when the through-hole 7 is a hole having a burr, the rib-shaped cut line 5a of the wire insertion tubular portion 5 may be caught by the projecting peripheral edge 7a, as shown in FIG. 9. Accordingly, the wire insertion tubular portion 5 may bend toward the vehicle body engagement recess 4 side and be wedged in between the peripheral edge 7a of the through-hole 7 and the vehicle body engagement recess 4. Such wedging of the wire insertion tubular portion 5 causes an incomplete fitting between the vehicle body engagement recess 4 of the grommet 1 and the peripheral edge 7a of the through-hole 7, resulting in an unsecured mounting of the grommet 1 in the through-hole 7.